What's stemming the adoption of 64-bit?

Adobe is going to provide the flash plugin for 64 bit Linux, before it provides it to 64 bit Windows or Mac OS X. Now, Microsoft says that a lack of 64 bit flash is preventing users from wholeheartedly adopting 64 bit, and a great number of macs are running 64 bit just fine (with 32 bit flash, because web applications should never need more than 4 GB of memory.) Now, if they just make the proprietary version easier to install under linux.